<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .box{
            width: 500px;
            height: 400px;
            background-color: pink;
            margin:100px auto;
            display: flex;
            flex-wrap: wrap;
            align-content: space-around;
            justify-content: space-around;
        }
        .box .item{
            width: 150px;
            height: 150px;
            background-color: blue;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
    </div>
</body>
</html>